Output match directional coupler

Abstract

A directional coupler that provides directional coupling and an impedance transformation is disclosed. In one embodiment, the directional coupler includes a low pass filter having a filter inductor that is coupled between an input port and an output port and a filter capacitor coupled between the output port and ground. The directional coupler also includes detector circuitry wherein the filter inductor is magnetically coupled to a detector inductor in the detector circuitry such that current passing through the filter inductor generates a detector current through the detector inductor. Furthermore, the low pass filter and the detector circuitry cooperate to transform a first impedance presented at the output port to a second impedance presented at the input port. Accordingly, the filter inductor is used in the low pass filter to provide an impedance transformation so as to operate with the detector circuitry to provide a detector current for directional coupling.

What is claimed is: 
     
       1. A directional coupler, comprising:
 an input port; 
 an output port; 
 a low pass filter comprising a filter inductor and a filter capacitor, wherein the filter inductor is coupled between the input port and the output port and has a first inductance and wherein the filter capacitor is coupled between the output port and ground; and 
 detector circuitry coupled to the filter inductor and comprising a detector inductor having a second inductance such that the first inductance of the filter inductor is greater than the second inductance of the detector inductor, wherein the detector inductor is magnetically coupled to the filter inductor such that current passing through the filter inductor generates a detector current through the detector inductor and wherein the low pass filter and the detector circuitry cooperate to transform a first impedance presented at the output port substantially to a second impedance presented at the input port. 
 
     
     
       2. The directional coupler of  claim 1  wherein the detector circuitry further comprises a coupled port coupled to the detector inductor and the detector circuitry is further configured so as to increase directivity between a forward signal voltage at the output port and a coupled voltage at the coupled port. 
     
     
       3. The directional coupler of  claim 1  wherein the detector circuitry further comprises a sampling capacitor coupled between the filter inductor and the detector inductor. 
     
     
       4. The directional coupler of  claim 1  wherein the detector circuitry further comprises a coupler termination coupled between the detector inductor and ground. 
     
     
       5. The directional coupler of  claim 1  wherein the detector circuitry is further configured to minimize power reflections. 
     
     
       6. The directional coupler of  claim 1  wherein the detector circuitry is further configured to balance the current across through the filter inductor with the detector current through the detector inductor. 
     
     
       7. The directional coupler of  claim 1  wherein the detector circuitry is coupled to the filter inductor by being connected to the output port. 
     
     
       8. The directional coupler of  claim 1  wherein the detector circuitry further comprises:
 a coupled port coupled to the detector inductor; 
 a sampling capacitor coupled between the output port and the detector inductor such that the detector inductor is coupled between the sampling capacitor and the coupled port; 
 a coupler termination coupled between the sampling capacitor and ground. 
 
     
     
       9. The directional coupler of  claim 8  wherein:
 the sampling capacitor is configured to provide a sampled voltage based on an output voltage at the output port such that the sampled voltage adjusts a first inductor voltage across the detector inductor; 
 the coupler termination having a termination impedance that provides a weight to the sampled voltage such that the current through the filter inductor and the detector current across the detector inductor are substantially balanced. 
 
     
     
       10. The directional coupler of  claim 8  wherein:
 the sampling capacitor is configured to provide a sampled voltage based on an output voltage at the output port such that the sampled voltage adjusts a first inductor voltage across the detector inductor; 
 the coupler termination having a termination impedance that provides a weight to the sampled voltage such that the output voltage at the output port is substantially balanced with a coupled voltage at the coupled port. 
 
     
     
       11. The directional coupler of  claim 8  wherein:
 the sampling capacitor is configured to provide a sampled voltage based on an output voltage at the output port such that the sampled voltage adjusts a first inductor voltage across the detector inductor; 
 the coupler termination having a termination impedance that provides a weight to the sampled voltage so as to increase directivity between a forward signal voltage at the output port and a coupled voltage at the coupled port. 
 
     
     
       12. The directional coupler of  claim 1  wherein:
 the detector circuitry is coupled to the filter inductor by being connected to an intermediate tap of the filter inductor; 
 a first portion of the filter inductor coupled between the input port and the intermediate tap is magnetically coupled to the detector inductor, wherein a third inductance of the first portion of the filter inductor is greater than the second inductance of the detector inductor. 
 
     
     
       13. The directional coupler of  claim 12  wherein a second portion of the filter inductor coupled between the intermediate tap and the output port is not magnetically coupled to the detector inductor. 
     
     
       14. The directional coupler of  claim 12  wherein the detector circuitry further comprises:
 a coupled port coupled to the detector inductor; 
 a sampling capacitor coupled between the intermediate tap and the detector inductor such that the detector inductor is coupled between the sampling capacitor and the coupled port; 
 a coupler termination coupled between the sampling capacitor and ground. 
 
     
     
       15. The directional coupler of  claim 14  wherein:
 the sampling capacitor is configured to provide a sampled voltage based on an intermediate voltage at the intermediate tap such that the sampled voltage adjusts a first inductor voltage across the detector inductor; 
 the coupler termination having a termination impedance that provides a weight to the sampled voltage such that the current through the filter inductor and the detector current across the detector inductor are substantially balanced. 
 
     
     
       16. The directional coupler of  claim 14  wherein:
 the sampling capacitor is configured to provide a sampled voltage based on an intermediate voltage at the intermediate tap such that the sampled voltage adjusts a first inductor voltage across the detector inductor; 
 the coupler termination having a termination impedance that provides a weight to the sampled voltage such that the intermediate voltage at the intermediate tap is substantially balanced with a coupled voltage at the coupled port. 
 
     
     
       17. The directional coupler of  claim 14  wherein:
 the sampling capacitor is configured to provide a sampled voltage based on an intermediate voltage at the intermediate tap such that the sampled voltage adjusts a first inductor voltage across the detector inductor; 
 the coupler termination having a termination impedance that provides a weight to the sampled voltage so as to increase directivity between a forward signal voltage at the intermediate tap and a coupled voltage at the coupled port. 
 
     
     
       18. The directional coupler of  claim 1  wherein the low pass filter and the detector circuitry cooperate to transform the first impedance presented at the output port to the second impedance presented at the input port when the first impedance is a first complex impedance. 
     
     
       19. The directional coupler of  claim 18  wherein the detector circuitry further comprises a coupler termination coupled between the detector inductor and ground and having a second complex impedance such that the low pass filter and the detector circuitry cooperate to transform the first complex impedance presented at the output port to the second impedance presented at the input port. 
     
     
       20. The directional coupler of  claim 19  wherein:
 the first complex impedance has capacitive reactance; and 
 the second complex impedance is inductive reactance. 
 
     
     
       21. The directional coupler of  claim 19  wherein:
 the first complex impedance has inductive reactance; and 
 the second complex impedance is capacitive reactance. 
 
     
     
       22. The directional coupler of  claim 1  integrated into an integrated circuit (IC) package that includes a laminated substrate and a semiconductor die mounted on the laminated substrate. 
     
     
       23. The directional coupler of  claim 22  wherein the detector circuitry further comprises a coupler termination coupled between the detector inductor and ground and wherein:
 the filter inductor and the detector inductor are formed by a metallic structure integrated into the laminated substrate; and 
 the coupler termination is formed by a Back End Of Line (BEOL) of the semiconductor die. 
 
     
     
       24. A method of providing directional coupling comprising:
 receiving an RF signal at an input port; 
 transforming a first impedance presented at an output port to a second impedance presented at the input port with a low pass filter and detector circuitry, wherein the low pass filter comprises a filter inductor and a filter capacitor, wherein the filter inductor is coupled between the input port and the output port and has a first inductance, and wherein the filter capacitor is coupled between the output port and ground; 
 generating a detector current through a detector inductor that is magnetically coupled to the filter inductor, wherein the detector inductor is provided by detector circuitry and the first inductance of the filter inductor is greater than a second inductance of the detector inductor; and 
 transmitting the RF signal from the output port once the RF signal is filtered by the low pass filter. 
 
     
     
       25. The method of  claim 24  further comprising increasing directivity between a forward signal voltage at the output port and a coupled voltage at a coupled port coupled to the detector inductor using the detector circuitry. 
     
     
       26. The method of  claim 24  further comprising minimizing power reflections with the detector circuitry. 
     
     
       27. An RF amplification device comprising:
 an RF amplification circuit to amplify an RF signal; 
 a directional coupler operably associated with the RF amplification circuit such that the RF amplification circuit presents an amplifier impedance to the directional coupler and configured to be coupled to a load such that the load presents a load impedance to the directional coupler, the directional coupler comprising: 
 a low pass filter comprising a filter inductor having a first inductance and a filter capacitor, wherein the filter inductor is coupled so that the RF signal passes across the filter inductor and the filter capacitor is coupled so as to be in shunt with respect to the load; and 
 detector circuitry coupled to the filter inductor and comprising a detector inductor having a second inductance such that the first inductance of the filter inductor is greater than the second inductance of the detector inductor, wherein the detector inductor is magnetically coupled to the filter inductor such that a detector current is generated through the detector inductor in response to the RF signal passing across the filter inductor and wherein the low pass filter and the detector circuitry cooperate to transform the load impedance to the amplifier impedance. 
 
     
     
       28. The RF amplification device of  claim 27  wherein the detector circuitry further comprises a coupled port coupled to the detector inductor and the detector circuitry is further configured so as to increase directivity between a forward signal voltage to the load and a coupled voltage at the coupled port. 
     
     
       29. The RF amplification device of  claim 27  wherein only the directional coupler is connected between the RF amplification circuit and the load. 
     
     
       30. The RF amplification device of  claim 27  wherein the detector circuitry is further configured to minimize power reflections between the load and the RF amplification circuit.